Along with recent widespread electronic apparatuses, the supply high-performance electronic apparatuses have been increasingly demanded. For example, conventional computers and communication controllers as exemplary electronic apparatuses have used gaskets that can be mounted onto a housing for resistance to electromagnetic waves from a printed plate (as disclosed, for example, in Japanese Patent Publication No. 8-274485). This gasket is required to have a physical structure to shield electromagnetic waves as well as a mechanical structure that facilitates mounting onto an electronic apparatus housing and prevents falling off from the housing.
A description will be given of a conventional gasket 10 with reference to FIGS. 20 and 21. Here, FIG. 20 is a perspective overview of the conventional gasket 10. As illustrated, the gasket includes a lid part 20 and an insertion part 30. Due to the lid part 20 and insertion part 30, the gasket 10 forms an approximately π shaped section. The insertion part 30 is a portion to be inserted into a housing, and includes a pair of support parts 32 each having an approximately rectangular parallelepiped shape, and a pair of engagement parts 34 each having an approximately right triangle pole shape.
FIG. 21 is a sectional view before and after the gasket 10 is inserted into a computer housing 2. The housing 2 has a perforation hole 4. Each support part 32 is slightly longer than the perforation hole 4 in the housing 2. The gasket 10 is made of an elastic member, and thus a pair of support parts 32 and engagement parts 34 deform so that they approach to each other while the gasket 10 is being inserted into the housing 2, and return so that they separate from each other after the engagement parts 34 project from the perforation hole 4.
As shown in FIG. 21, when the gasket 10 is inserted into the housing 2, the lid part 20 contacts a top surface 6 of the housing 2, the support parts 32 of the insertion part 30 are located in the perforation hole 4, and the engagement parts 34 project from a bottom surface 8 of the housing 2, so that bracket parts 35 contact the peripheral of the perforation hole 4. When the engagement parts 34 contact the bottom surface 8, the lid part 20 applies an elastic force as a flat spring to the housing 2.
Thus, the conventional gasket 10 is configured so that once it is inserted into the housing 2, the bracket parts 35 of the engagement parts 34 are hooked on the bottom surface of the housing 2 even when it is attempted to be pulled out and it does not come off easily.
FIG. 22 is a graph of exemplary reactions in mounting the gasket 10 onto and pulling off the gasket 10 from the housing 2. FIG. 22 shows results of two experiments F1RF2 and F2RF2. As illustrated, it is understood that the mounting reaction is 360 g (180 g ×2) per width, and the puling-off reaction is 140 g (70 g ×2) per width. This means that the pulling-off force is smaller than the mounting force and the gasket 10 is easily pulled off. In other words, the conventional gasket 10 has not had such a structure as meets a mechanical requirement of easy mounting and hard pulling off. When the gasket 10 comes off electromagnetic waves and noises leak from a printed circuit board in an electromatic apparatus, undesirably causing, for example, a t levision around the electronic apparatus to distort screen images. In addition, the coming-off gasket 10 also causes a problem of a loss due to its small size. Therefore, it is preferable that the pulling force is larger than the mounting force and the mounting force is as small as possible.